In order to detect single nucleotide polymorphisms (SNPs) considered to provide information useful in a genetic diagnosis, a made-to-order therapy, a tailor-made therapy, or the like, a difference between a Tm value obtained at the time of the matching of a base pair (at the time of the formation of a perfect complementary strand) and a Tm value obtained at the time of the mismatching of the base pair (at the time of the formation of an imperfect complementary strand) (hereinafter referred to as “ΔTm value”) is considered to be preferably as large as possible. In particular, when the ΔTm value is 10° C. or more, it has been known that an excellent diagnostic method in which a misdiagnosis rate at the time of a genetic diagnosis based on a single nucleotide polymorphism is less than 1% can be provided.
In recent years, a peptide nucleic acid known as one kind of nucleic acid analogs has been attracting attention from the viewpoint of its high stability. The development of a technology involving detecting a single nucleotide polymorphism with such peptide nucleic acid has been advanced (Non Patent Literatures 1 and 2).
With regard to the technology involving detecting a single nucleotide polymorphism with a peptide nucleic acid, such peptide nucleic acid as described in Non Patent Literature 2 does not show a ΔTm value enough to detect a single nucleotide polymorphism. Specifically, its ΔTm value when a mismatch is present in the base of a target DNA strand positioned second from an N-terminal is about 6.4° C. or less.